Algorithms for Separation of Secondary Surveillance Radar Replies

Air Traffic Control (ATC) centers aim at ensuring safety of aircrafts cruising in their area. The information required to face this mission includes the data provided by primary and Secondary Surveillance Radar (SSR). The first one indicates the presence of an aircraft, whereas the second gives information on its identity and altitude. All aircrafts contain a transponder, which send replies to the secondary radar in a semi-automatic mode, indeed it is an exchange. The increase of the air traffic implies that in a near future the actual SSR radar will not be able to perform correctly, and that requires to improve the quality of the SSR radar. This thesis proposes a possible improvement of the SSR. We propose to replace at reception the rotating antenna by an antenna array to gain spatial diversity, in order to perform beamforming. Given the density of the traffic, high-resolution techniques are mandatory to separate the sources. This is a blind source separation problem, but unlike standard cases, the sources are sending packets (not continuously), the packets do not completely overlap (non-stationary situation), the alphabet is binary but not antipodal ({0, 1} instead of {+1,â1}). And the carrier frequencies are not identical. Among the problems to solve, two main issues are the non- synchronisation of the sources, and the non-calibration of the antenna. This thesis presents new contributions to this field, including the identifiability of parameters and related Cramer-Rao bounds, and the design of receiver algorithms taking into account the specific encoding of the data (such as the MDA and the ZCMA algorithms presented herein). The performance of these algorithms is tested by extensive computer simulations as well as actual measurements; the setup of the experimental platform is also part of the thesis framework.Applied Science